5.1 Classifying rocks

Vocabulary

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1.Grains:-A particle of mineral or other rock that gives a rock a texture
2.Texture:-The look and fell a rock's surface determined by the size ,shape,and a pattern of a rock grains
3.Igneous rock:-A type of rock that forms from the cooling of molten rock at or below the surface.
4.Sedimentary rock:-A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together.
5.Metamorphic rock- A type of rock that forms from an existing rock that is changed by heat,pressure or chemical reactions

Outline

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How Geologists classify rocks

• On Earth, rocks forms mountains, hills, valleys, beaches even the ocean floor.
  • Earth's crust is made of rock.
    • Geologists collect and study samples of rock in order to classify them.
    • When studying a rock sample, geologist observe rocks color and texture and determine its mineral composition.

Texture

• A rocks texture is very useful in identifying the rock.
  • Some rocks are smooth and glassy.To describe a rock's texture, geologists use a number of terms based on the size and pattern of the rock's grains.

Mineral Composition

• Often geoligist must look more closely at a rock to determine its mineral composition.
  • To prepare a rock for viewing under the microscope, geologist cut the rock very thin, so that light can shine through its crystals.

origin

• There are three major groups of rocks:igneous rock,sedimentary rock, and metamorphic rock.
  • Rocks belonging to each of thesedifferent forms in different way.